Study On Ablation And Plasma Characteristics Of A Laser-Assisted Pulsed Plasma Thruster

Combining laser technology and electromagnetic acceleration technology,the laser-assisted pulsed plasma thruster（LA-PPT）significantly improves the propulsion performance of electric propulsion thrusters.However,as a new type of electric thruster,the mechanism of laser-polymer interaction and plasma evolution is still unclear.Therefore,to deeply understand the mechanism of LA-PPT,it is necessary to conduct numerical and experimental research on the ablation characteristics and plasma characteristics of the thruster.The short pulse laser ablation model of polyvinyl chloride（PVC）has been established.The physical and chemical processes such as the thermal decomposition reaction,the variation of physical parameters with temperature,the influence of non-Fourier effect,and the remove of phase transition and ablation interface are considered.The simulation result reveals the effects of laser intensity,absorption coefficient,thermal relaxation time and reflectivity on the laser ablation process of PVC.The result plays an important guiding role in further modifying LA-PPT target and improving the utilization rate of target.Owing to the short-time discharge and the novel configuration,the physical mechanism of the discharge is unclear.Time and spatial-resolved optical emission spectroscopy was applied to investigate the variation in the plasma properties in the thruster discharge channel.The plasma species,electron temperature,and electron density were obtained and discussed.Our investigation revealed that there were Hα,Hβ,Hγ,Hεatoms,C I,C II,C III,C IV,Cl I,Cl II particles,and a small amount of CH,C₃,C₂,H₂neutral molecular groups in the plasma.The electron temperature of the discharge channel of the thruster was within 0.6–4.9 e V,and the electron density was within 1.1–3.0×10¹⁸ cm^-3.The temporal and spatial evolution characteristics of plasma are analysed according to the plasma diagnosis results.Unlike the conventional PPT,which has high electron density near the thruster surface,LA-PPT shows high electron density at the thruster outlet,which increased the thruster specific impulse.